The present invention pertains generally to chemical lasers that use Iodine gas as an input stream. More particularly, the present invention pertains to systems for producing contaminant free Iodine gas for use in a chemical laser. The present invention is particularly, but not exclusively, useful as an on-demand, Iodine supply system that produces an Iodine gas that is free of water, Carbon Monoxide and Carbon Dioxide contaminants.
The Chemical-Oxygen-lodine-Laser (COIL) is potentially useful for both military and commercial applications because it is capable of producing a high power laser beam. In the COIL process, Iodine gas is combined with singlet delta Oxygen in a laser cavity to produce a laser beam. Iodine, however, is a solid at room temperature. It must therefore be vaporized to produce the Iodine gas required in the COIL laser cavity. The All Gas Iodine Laser (AGIL) similarly requires an Iodine vapor source.
One method for producing Iodine gas involves melting Iodine in an Iodine reservoir. The Iodine vapors that are given off by the molten Iodine are then transported using a carrier gas to the laser cavity through a delivery system. In general, the required delivery system involves piping and other complex parts such as valves, precision orifices, and temperature and pressure instruments. Unfortunately, this method of producing gaseous Iodine has several drawbacks. For instance, the entire delivery system, including the carrier gas, must be preheated and maintained at elevated temperatures to prevent Iodine condensation from plugging the delivery system. For a typical COIL system that is designed for military applications, several hours are required to melt the Iodine and preheat the delivery system. On the other hand, the source for generating the singlet delta Oxygen that is to be combined with the Iodine gas requires only a fraction of a minute to reach operational status.
In the molten and gaseous states, Iodine is extremely corrosive. Because of lodine""s corrosivity, equipment exposed to Iodine, such as the Iodine reservoir and delivery system described above, must be fabricated from expensive materials such as Hastelloy C-276. In addition to degrading any exposed equipment, the corrosion reaction will, with time at temperature, contaminate the Iodine in the reservoir, requiring the Iodine in the reservoir to be periodically purified or discarded. Impurities in the Iodine must be maintained at very low levels as they may be transported to the laser cavity where they can coat the optical components. For military applications, where readiness is important, a reservoir of molten Iodine would be required at all times, leading to a significant amount of corrosion. Furthermore, the delivery system valves, which must be operated hot and in the presence of Iodine, will deteriorate with time at temperature and leak allowing corrosive Iodine to escape. Such a leak could be potentially harmful to electronic equipment. For these reasons, in order to perform routine maintenance on the molten Iodine reservoir and delivery system, these systems must be periodically shut down and allowed to cool. Additionally, maintenance of liquid Iodine systems creates a large amount of Iodine contaminated waste that requires special handling and disposal. In summary, the molten Iodine reservoir and delivery system is large, heavy, costly and complex.
The present invention recognizes that a gas containing Iodine can be generated by the combustion of a solid fuel/oxidizer mixture that contains Iodine. By using a solid source of Iodine, many of the problems associated with the use of liquid Iodine are eliminated and a supply of gaseous Iodine can be quickly produced. Examples of fuel/oxidizer systems that can be reacted to produce gaseous Iodine include the CI4/Iodine Pentoxide (I2O5) system and the CHI3/I2O5 system. Unfortunately, these fuel/oxidizer systems have the potential to produce gaseous contaminants including water, Carbon Monoxide and Carbon Dioxide. These contaminants, if present in sufficient quantities, can unacceptably degrade the performance of a COIL laser system.
In light of the above, it is an object of the present invention to provide a system for supplying Iodine gas for use in a chemical laser wherein the Iodine gas is free of water, Carbon Monoxide and Carbon Dioxide contaminants. It is another object of the present invention to provide an on-demand, contaminant free Iodine gas supply system for a chemical laser that does not require a liquid Iodine reservoir to be maintained during periods of non-demand. It is still another object of the present invention to provide an on-demand, Iodine gas stream that is free of entrained solids, water, Carbon Monoxide and Carbon Dioxide. Yet another object of the present invention is to provide an on-demand contaminant free, Iodine gas supply system which is easy to use, relatively simple to implement, and comparatively cost effective.
The present invention is directed to an on-demand system for generating Iodine gas that is substantially free of contaminants such as water, Carbon Monoxide and Carbon Dioxide. Once generated, the contaminant free Iodine gas can be used as an input stream for a chemical laser such as a Chemical-Oxygen-lodine-Laser (COIL). More specifically, the contaminant free Iodine gas can be combined with singlet delta Oxygen in the laser cavity of the COIL to efficiently produce a high power laser beam. For the present invention, the system for generating contaminant free Iodine gas includes a solid mixture of oxidizer and fuel. An ignitor squib is provided to ignite the mixture and thereby generate a contaminant free Iodine gas.
In greater detail, the solid mixture contains at least one Iodine compound. The Iodine compound can be present in either the oxidizer, the fuel or both. Importantly, the mixture is substantially free of Hydrogen and Carbon compounds. In one embodiment of the present invention, Iodine Pentoxide (I2O5) is used as the oxidizer and a metal such as is Zinc, Tin, Calcium, Magnesium, Aluminum, Silicon, Sodium, Potassium, Lithium, Boron, Beryllium or Iron is used as the fuel. Alternatively, the fuel may be a compound, that generates additional Iodine, such as metallic Magnesium Iodide or a metallic compound that generates an inert gas, such as Sodium Azide. A preferred embodiment uses Zinc metal for the fuel and Iodine Pentoxide (I2O5) as the oxidizer. Another preferred embodiment uses Sn metal for the fuel and Iodine Pentoxide (I2O5) as the oxidizer. A third preferred embodiment uses Sodium Azide (NaN3) as the fuel and Iodine Pentoxide as the oxidizer.
Upon ignition of the fuel/oxidizer mixture, the reaction products include Iodine gas with little or no water, Carbon Dioxide or Carbon Monoxide. In addition, the reaction products include metal oxides that are generally created in either the solid or liquid state. In preferred embodiments of the present invention, precautionary measures are taken to prevent the metal oxides from becoming entrained in the gaseous Iodine stream and contaminating the laser cavity. For example, in one embodiment of the present invention, the mixture is disposed within a permeable jacket. During combustion, the solid oxides are captured by the permeable jacket while the Iodine gas passes through the permeable jacket for subsequent delivery to the laser cavity. In accordance with the present invention, the permeable jacket is preferably made of a fibrous ceramic, quartz wool or fiber glass.
The permeable jacket can be used to capture both solid and liquid metal oxides. For fuel/oxidizer combinations that react to produce liquid metal oxides, a slagging agent such as Sodium Silicate, Silica, Alumina, Magnesia, Borax, Calcia or Sodium Borate can be included in the solid mixture to form a slag of the liquid metal oxides. The slagging agent may also be incorporated in the oxidizer (e.g. Magnesium lodate). For some applications, it is preferable to form liquid metal oxides rather than solid metal oxides. For this purpose, two or more metal fuels (such as a combination of Zinc and Tin or Zinc and Silicon) may be-used in the solid mixture. By combining two or more selected metal fuels in the mixture, an oxide combination having a relatively low melting point is generated during combustion (i.e. a combination of oxides having a melting point lower than each of the individual oxides can be obtained).